1. Field of the Invention
The present invention relates to a multiplexing/demultiplexing apparatus for wavelength division multiplexed system and wavelength division multiplexed passive optical subscriber networks using the same apparatus, and in particular to a multiplexing/demultiplexing apparatus, which performs simultaneous multiplexing and demultiplexing of signals in each direction using a multiplexing/demultiplexing means for economical implementation of the optical subscriber networks, and wavelength division multiplexed passive optical subscriber networks using the same apparatus.
2. Description of the Conventional Art
Wavelength division multiplexed (WDM) passive optical subscriber networks (PON""s) offer the potential of large capacity, network security, and upgradability. However, these prior networks require low-cost sources, and efficient routing at the central office and remote nodes for practical implementation.
Generally, optical subscriber networks minimize the length of optical lines by using double-star structure. Namely, a connection between a central office and a remote node placed at the neighboring area of subscribers is made by one optical fiber, and connections between the remote node and each subscriber are made by individual optical fiber. Wavelength division multiplexed mode, in which each subscriber uses different wavelength from each other, can distinguish each subscriber using wavelength. The central office and remote nodes, therefore, need both a multiplexing apparatus that multiplexes wavelength divided optical signals and a demultiplexing apparatus that demultiplexes multiplexed optical signals. Such apparatuses use waveguide grating router (WGR) or devices with the same function as it.
The conventional wavelength division multiplexed passive optical subscriber networks are disclosed in the U.S. Pat. No. 5,550,666 entitled xe2x80x9cWavelength division multiplexed multi-frequency optical source and broadband incoherent optical sourcexe2x80x9d and in the U.S. Pat. No. 5,574,584 entitled xe2x80x9cWavelength division multiplexing passive optical network with bi-directional optical spectral slicingxe2x80x9d.
In addition, as another conventional wavelength division multiplexed passive optical subscriber networks, there is the paper of Stuart S. Wagnar and Howard L. Lemberg, xe2x80x9cTechnology and system issues for a WDM-based fiber loop architecturexe2x80x9d, J. Lightwave Technol., vol. 7, no. 11, pp. 1759-1768, 1989.
The conventional wavelength division multiplexed passive optical subscriber networks need separate multiplexer and demultiplexer each in up direction and down direction for bi-directional communication. This causes to increase system costs and to waste system resources.
Accordingly, it is an object of the present invention to provide a multiplexing/demultiplexing apparatus for wavelength division multiplexed system, which is capable of implementing economical and efficient wavelength division multiplexed passive optical subscriber networks, and wavelength division multiplexed passive optical subscriber networks using the same apparatus, by employing two WGR""s, one at the central office and one at the remote node, and performing simultaneous multiplexing and demultiplexing of signals in up and down direction.
To achieve the above object, there is provided a multiplexing/demultiplexing apparatus used in wavelength division multiplexed passive optical subscriber networks according to the present invention which includes a multiplexing/demultiplexing means each having N, a natural number, input and output ports, wherein wavelength divided signals in one direction inputted through the Nxe2x88x921 input ports are multiplexed onto one output port, and simultaneously wavelength division multiplexed signals in the other direction inputted through the remainder one input port are demultiplexed onto the remainder Nxe2x88x921 output ports.
To achieve another object, there are provided wavelength division multiplexed passive optical subscriber networks including a central office, and one or more remote nodes which are coupled to the central office by way of an optical fiber and further are coupled to a plurality of subscriber""s units by way of an optical fiber, wherein
the central office comprises: a first optical signal generating means for generating an optical signal; a multi-channel signal generating means for generating Nxe2x88x921 wavelength divided channel signals using the optical signal generated by the first optical signal generating means; Nxe2x88x921 modulating means each for modulating the channel signals generated by the multi-channel signal generating means; a first multiplexing/demultiplexing means each having N input and output ports, wherein wavelength divided signals inputted from the each modulating means through the Nxe2x88x921 input ports are multiplexed onto one output port, and simultaneously wavelength division multiplexed signals inputted from the remote node through the remainder one input port are demultiplexed onto the remainder Nxe2x88x921 output ports; and Nxe2x88x921 first detection means each coupled to said Nxe2x88x921 output ports of the first multiplexing/demultiplexing means for receiving the demultiplexed channel signals of said each subscriber,
the remote nodes comprise: a second multiplexing/demultiplexing means each having N input and output ports, wherein wavelength division multiplexed signals inputted from the central office through one input port are demultiplexed onto Nxe2x88x921 output ports, and simultaneously signals inputted from the each subscriber""s unit through the remainder Nxe2x88x921 input ports are multiplexed onto the remainder one output port,
the subscriber""s unit comprises: Nxe2x88x921 second detection means each for receiving the signals demultiplexed by the second multiplexing/demultiplexing means; and a second optical signal generating means for generating an optical signal.